This project will analyze the cellular and molecular heterogeneity of various types of human melanoma-associated antigens identified with monoclonal antibodies and assess the clinical significance of distinct epitopes expressed on each type of human melanoma-associated antigen. Several immunization approaches will be used to develop a library of monoclonal antibodies to the various determinants (individual, cross-reacting, framework and xenogeneic) of the different types of tumor-associated antigens expressed on human melanoma cells. The specificity of these antibodies will be assessed by serological and immunochemical assays with cell lines and with surgically removed tissues. Antibodies reacting with different determinants of melanoma-associated antigens will be tested individually and in combination for their ability to mediate complement dependent and cell dependent lysis of melanoma cells--thus establishing the role of different epitopes of melanoma-associated antigens in the immune lysis of tumor cells. Monoclonal antibodies will be used to purify immunologically functional melanoma-associated antigens which will be analyzed for their structural properties, with special emphasis on their glycoprotein or glycolipid nature, subunit structure, molecular heterogeneity (identified by the distribution of antigenic determinants recognized by monoclonal antibodies on subpopulations of molecules within each type of melanoma-associated antigen) and the structural basis underlying this heterogeneity. The biosynthesis, processing and shedding of various types of melanoma-associated antigens will be investigated to aid our understanding of the in vivo interaction between tumor cells and the immune system of the host. Biopsies of malignant lesions from melanoma patients will be phenotyped with our library of monoclonal antibodies, and the results will be correlated with the clinical course of the disease and with response to therapy. The results from our studies will aid the characterization of the molecular basis of malignant transformation of human cells and will assess the usefulness of monoclonal antibodies in clinical oncology.